Drilling ball bearings

Your list of requirements reminds me of a sign I saw behind the counter of a shop: "Price, quality, speed. Pick any two."

I drilled a couple once - to make a ball & socket linkage. I annealed them first and they drilled easily. HOWEVER, they did not have a polished look afterwards. You could try annealing a couple and then see how much work it is to get the polished look back.

Bob

I just happen to have an EDM that we are only tinkering with, hasn't done any production yet..

A friend of mine taught me that expression

Good, Fast, Cheap...Pick Two

Finding someone with an EDM machine or two knocking around is what I'd choose.

GTO(John)

If you're going to do a thousand of them, and you're paying for it, it had better be a hole-popping EDM. A standard sinker would be too slow.

Ed Huntress

Ed, I don't doubt that you are correct, that a hole-popper is faster but, why is that so??? Does it have to do with set-up? Why wouldn't the amps determine the rate of erosion - whether it's a hole-popper or sinker?

Which sinker EDM would you recommend for a beginner? TIA.

The hole-popper, which first came along around 1982, is a rough-and-fast sinker machine with a power supply set up for blasting metal away as fast as possible. The electrode wear rate is horrible, but it doesn't matter. The electrodes are just small tubes. And the accuracy is 'way too rough for EDMing accurate cavities.

Yes, the amps are the basic determinant of eroding rate, but it's the mean amperage that counts, for the most part. It's not a straight-line relationship, but it's close enough. Hole-poppers put a lot of average amperage into the cut and count on cooling from the electrolyte (usually water for hole-poppers, or, at least, that's what they used at first) to keep the electrode from getting too hot.

If it's for commercial use, the best modern CNC machine you can afford. If it's for hobby work, I guess the newest you can afford. Newer ones are capable of more speed and much greater accuracy. They're also a hell of a lot easier to run than the old ones.

What applications do you have in mind?

-- Ed Huntress (remove "3" from email address for email reply)

Ack! I said "electrolyte." I should have said "dielectric." Distilled water is the dielectric. Electrolytes are used in ECM, not in EDM.

The water can get loaded with metal ions in wirecut EDM and in hole-poppers, which will, under some conditions, increase the cutting rate. The machine does some electrochemical machining along with its spark-discharge eroding. But it's not considered desirable, even though there are some additives available for the water that are intended to enable some electrochemical action. In general, it's not a subject for beginning EDMers to fool with.

-- Ed Huntress (remove "3" from email address for email reply)

Thank you. Your answer explains why they sell hole-poppers, in addition to sinkers.

What I'd like to have is a sinker for shoe-box size mold bases...... that is, soft-ball size cavities....... not for commercial use...... not for artificial hearts ...... more for chalk-lines and anchor bolt holders/ construction stuff. I'm leaning toward..... new ...... $25,000+/-...... maybe Chevalier ED252..... although I'd prefer American made ......... in lieu of a boat or a plane, both of which seem pointless.

Just buy some ball and socket parts Why reinvent the wheel?

In my case I needed a very short linkage (3"+-) which had to include a ball joint on each end.

You may want to ask this question on alt.machines.cnc. There are some moldmakers there who could give you recommendations about current models. I suspect, though, the same thing that you seem to suspect: you're probably looking at an import. EDMs are a catagory in which foreign machines have most segments of the market wrapped up. I'm not even sure what EDMs are being made in the US these days. I've sort of lost touch with the field over the last three years or so. I don't really cover it anymore.

In any case, your requirements don't sound very demanding, and you probably could use any of a variety of different machines for that work, including some used machines dating back 15 years or a little more. The finesse required for precision and ready-to-run finished surfaces are better handled by the latest and greatest, but everything is a tradeoff. If you give some specific examples of the work to some moldmakers, you'll get good answers.

Good luck!

Ed Huntress

Doesn't sound like what you're looking for, but have you tried here yet?

Wayne

On Mon, 1 Sep 2003 13:52:14 -0700 (PDT), dann mann wrote in Msg.

No, I know all those things and they don't work. Actually, the things on this website are pretty much what I need:

Why don't I buy from this guy? I have, and I'm happy with the product, only there are a few catches (irrelevant to the discussion) that make me look into getting these joints locally, more quickly, and less expensive. Of course I've also found local mechanics that would make me the clamp parts for a considerably lower price, but it's the balls that this problem hinges on, so to speak.

--Daniel